The present invention relates to laminated structures, and particularly to such structures which are fabricated of layers of filament composite material.
Fiber reinforced composite materials, such as filament woven or wound laminates, are replacing metal materials in many areas such as aerospace applications due to their excellent structural performance and low fabrication costs. In aerospace applications, filaments fabricated of glass composite materials considerably reduce the weight of structural components in vehicles where metallic materials are predominant. Such lightweight composite materials offer such advantages to aircraft designers, for instance, and their use is expected to increase dramatically simply as increased confidence in their reliability is established. However, problems are associated with such composite materials due to their vulnerability to lightning strike damage and electromagnetic interference. Consequently, there is a need to provide filament reinforced composite materials which can withstand lightning strikes or shield internal components from electromagnetic interference.
The conductivity of some composite materials, such as graphite, is sufficient in certain low order applications, but, in general, the conductivity of such materials is insufficient to combat lightning strike damage or to shield against high electromagnetic interference.
Attempts have been made to provide filament reinforced composite materials with the electrical conductivity which is prevalent with metal materials presently used for structural components, such as in the aerospace industry. For instance, some techniques employed to achieve a conductive surface have included painting the surface with a metal-based paint, bonding metal foil to the surface, flame-spraying metallic coatings, using metal wire mesh layers, and incorporation of metal strips or studs in the structural component. However, all of these attempts to provide a conductive media in a composite structure require secondary or additional operations resulting in higher costs of the respective structure.
The present invention is directed to solving the above described problems and to satisfy the need of providing a conductive media in composite structures to provide a structure with protection against lightning strike damage, electromagnetic interference.
In general, the present invention contemplates a composite structure, such as a structural component in an aerospace vehicle, which is fabricated of non-metallic filament laminates, with certain of the filaments coated with a conductive metal, such as aluminum, which will provide a conductive media. The coated filaments are intermixed with resin and are cured simultaneously with the entire structure resulting in superior structural performance and lower cost.
In particular, the present invention contemplates a laminated structure, such as a structural component of an aerospace vehicle or the like, which is fabricated of layers of filament composite material. The outer surface layer of the filament composite material is fabricated of conductive metallic-coated filaments to provide protection against lightning strike damage and electromagnetic interference. The outer surface layer of coated filaments provides a conductive barrier to disperse the current from lightning or other electromagnetic sources. Preferably, one or more outer surface layers are fabricated of the coated filaments, but not the entire thickness of the filament composite material comprising the structural component.
In the preferred embodiment of the invention, the filaments are fabricated of a composite material such as glass, or Kevlar, and the filaments are coated with an aluminum material. It is contemplated that the laminated structure may be filament wound with the outer surface layer thereof being wound with the conductive metallic-coated filaments. The laminated structure and outer surface layer also may be fabricated in a woven fashion. A wide variety of patterns of filament or fiber content for the laminated structure is contemplated, with the outer surface layer thereof fabricated of the conductive metallic-coated filaments. The entire composite structure, including the outer surface layer of coated filaments, can be intermixed or impregnated with epoxy resin, and the entire laminated structure can be cured simultaneously. This eliminates any secondary or additional operations which is prevalent with prior attempts to provide a conductive media in a filament composite structure.
Other objects, advantages and features of the invention will be apparent from the following detailed description taken in connection with the accompanying drawings.